Formularization of the confinement enhancement factor as a function of the heating profile for FFHR-d1 core plasma design

Abstract

A quantitative estimation of the confinement enhancement due to the heating profile effect is introduced to the helical fusion DEMO reactor design of FFHR-d1, based on the experimental results of the Large Helical Device. By applying this to the direct profile extrapolation (DPE) method, radial profiles in the reactor are extrapolated from experimental results. In reactor plasmas, the heat deposition profile of alpha heating is expected to be peaked in the core region as in the case of tangential neutral beam (NB) injection on low-density plasmas. The height of the pressure profile normalized by the gyro-Bohm-type parameter dependence increases with the power (∼0.6) of the peaking factor of the heat deposition profile, as long as the core confinement degradation observed in low-density plasmas is ignored. According to this observation, the confinement enhancement factor expected under the self-ignition condition ranges from ∼1.1 to ∼1.7, for example, depending on the used data. Degradation of the global energy confinement observed in high-density NB-heated plasmas is mitigated and the gyro-Bohm-type parameter dependence reappears after introducing the confinement enhancement due to the heating profile effect. Finally, typical example profiles in FFHR-d1 are provided by the DPE method for future analyses.

Potential of Copper Alloys using a Divertor Heat Sink in the Helical Reactor FFHR-d1 and their Brazing Properties with Tungsten Armor by using the Typical Candidate Filler Materials

“…The intrinsic structure of the FFHR-d1 is similar to the Large Helical Device (LHD) [5]. While device size is four times larger than the LHD, the major radius (R) is R = 15.6 m [6][7][8]. In the case of the heliotron type devices, the edge magnetic structure is more complicated than the tokamak devices, and an intrinsic divertor exists without additional coils [9].…”

Maintainability of the helical reactor FFHR-c1 equipped with the liquid metal divertor and cartridge-type blankets

“…Both scalings show the socalled gyro-Bohm property, as is also recognized in the scalings for tokamaks [14]. The plasma parameters in FFHR-d1 have been estimated by using the Direct Profile Extrapolation (DPE) method, which is based on the gyro-Bohm model [9,[15][16][17][18]. According to the DPE method, two devices having an identical value of Rc Bc 3/4 can Fig.…”

Novel features of the helical volumetric neutron source FFHR-b2

“…The FFHR-b2 is basically a beam-plasma fusion reactor, where 80 keV -5 MW tangential D beam is injected to the target DT plasma, of which the T ratio is changed from 0 to 100 %. The fusion output is estimated by an iterative calculation as follows; (1) determine the ion and electron temperature profiles by the DPE (Direct Profile Extrapolation) method [28][29][30][31] using assumed ion and electron density profiles and a heat deposition profile of NBI, (2) calculate the magnetic equilibrium by the VMEC code [32] using the pressure profiles obtained, (3) calculate the NBI heat deposition profile and the birth profile of alpha particles generated by the beam-plasma fusion reaction by the FIT3D code [33] using the magnetic equilibrium, (4) return to (1) and recalculate the temperature profiles, and then repeat the procedure from (1) to (4) until the temperature profiles converge, (5) recalculate the heat deposition and pressure profiles of NBI and alpha particles by the GNET code [34][35][36] using the converged temperature profiles, (6) return to (1) and recalculate the temperature profiles, and then repeat the procedure from (1) to ( 6) until the temperature profiles and magnetic equilibrium converge. In this study, the last iteration was not necessary because the magnetic equilibrium obtained using the GNET results were already well converged.…”